There are several principles of design that can add visual interest to a work, but one of the most important principles in this regard is contrast.
Contrast refers to the use of different elements in a work to create visual interest and variation. This can include using contrasting colors, shapes, textures, sizes, or other design elements to create a dynamic and engaging composition. By juxtaposing different elements, contrast can create a sense of tension, energy, and movement in a work, drawing the viewer's eye and adding visual interest.
Other principles of design that can add visual interest to a work include balance, emphasis, unity, rhythm, and proportion. Each of these principles plays a role in creating a compelling and visually engaging design, and they are often used in combination with one another to create a cohesive and effective composition.